I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 20101 Experimental study of PFCs erosion and...
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Transcript of I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 20101 Experimental study of PFCs erosion and...
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 1
Experimental study of PFCs erosion and eroded material deposition under ITER-like transient
loads at plasma gun facility QSPA N. Klimov1, V. Podkovyrov1, A. Zhitlukhin1, D. Kovalenko1, J. Linke2,
G.Pintsuk2, I. Landman3, S. Pestchanyi3, B. Bazylev3, G. Janeschitz3, A. Loarte4, M. Merola4, T. Hirai4, G. Federici5, B. Riccardi5, I. Mazul6,
R. Giniyatulin6, L. Khimchenko7, V.Koidan7
1SRC RF TRINITI, ul. Pushkovykh, vladenie 12, 142190, Troitsk, Moscow Region, Russia2Forschungszentrum Jülich GmbH, EURATOM Association, D-52425 Jülich, Germany
3Karlsruhe Institute of Technology, P.O. Box 3640, 76021 Karlsruhe, Germany (KIT)4ITER Organization, St. Paul-lez-Durance, F-13108 Cadarache, France
5Fusion for Energy, ITER Department, Josep Pla, 2, Torres Diagonal Litoral B3, 08019 Barcelona, Spain6Efremov Institute, 196641, St. Petersburg, Russia
7RRC «Kurchatov Institute», Moscow, Russia
Troitsk Institute for Innovation and Fusion Research
F4E EfremovInstitute
RRCKurchatovInstitute
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 2
Outline
• Experimental facilities, targets, diagnostics
• ELMs simulation experiments at low heat loads
• Mixed materials and erosion products investigation
• Conclusion
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 3
Experimental facilitiesQuasistationary plasma accelerator
QSPA plasma parameters (ELMs):
• Heat load 0.5 ÷ 5 MJ/m2
• Pulse duration 0.1 ÷ 0.6 ms• Plasma stream diameter 6 cm• Ion impact energy 0.1 ÷ 1.0 keV• Electron temperature < 10 eV• Plasma density 1022 ÷ 1023 m-3
QSPA plasma gun
1 – coil of pulse electromagnetic gas valve;2 – valve disk; 3 – volume of pulse valve;4 – isolator; 5 – gas supply tube;6 – cathode; 7 – anode.
QSPA facility provides adequate pulse durations and energy densities. It is applied for erosion measurement in conditions relevant to ITER ELMs and disruptions
QSPA-T facility QSPA-Be facility
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 4
Experimental conditionsTarget design
CFCSNECMA NB31
pure W orW-1% La2O3
Special 31 ITER-like targets (6 CFC, 3 pure W, 6 W-1%La2O3, and 16 Ве) • were designed and manufactured by EU• were pre-characterized by Forschungszentrum Jülich (Germany) by optical / electron microscopy
and laser-profilometry
3(7)2
5
2020
W – grain orientation orCFC - pitch fibre orientation
Cu
SS
CFCSNECMA NB31
15019.5
19.5
60
9.5
9.5
W (>99,96%) и
W-1% La2О3
Be-clad and Be-coated
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 5
Experimental conditionsScheme of PFCs testing
• Target was preheated up to 500O C • Plasma pulse duration was t = 0.5 ms• Plasma-surface angle α = 300
• Total number of pulses was up to 1000 for ELMs experiments and up to 10 for disruptions experiments• Absorbed energy density at plasma axis was
0.5÷1.5 MJ/m2 in ELMs experiments2.3 MJ/m2 in disruption experiments
View of the target on a heater
Plasma flow
Castellated tungsten (or CFC) target
60O
Absorbed energy density profile
Target orientation
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 6
DiagnosticsMeasurements of absorbed energy density distribution
25
180
90
15
X
Y
110
195
Cells with thermocouplesShield frame
Plasma facingsurface (CFC)10x10 mm2
Surface connected to thermocouple
Copper layer
Absorbed energy density distribution was measured by means of special CFC and tungsten target-like calorimeters
Schemes and views of the calorimeters
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 7
Experimental conditionsAbsorbed energy density distribution
Typical energy density profile on W surface The energy density distribution on W surface,%
The energy density distribution on CFC surface,%Typical energy density profile on CFC surface
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 8
DiagnosticsPlasma parameters
measurementsPFCs erosion measurement
Products erosion study
1. Pressure probe
2. System of plasma stream velocity measurements
3. Calorimeters
1. Microbalance
2. Mechanical profilometer
3. Laser profilometer
4. SEM with X-ray analysis
5. IR-cameras
6. Optical microscopes
1. Online diagnostics for dust particle ejection study
2. Dust collectors
3. Quartz crystal microbalance
4. Optical microscopes
5. SEM with X-ray analysis
Plasma pressure, plasma flow duration, plasma stream velocity, ion impact energy, plasma flow energy density, absorbed energy density
Mass losses, erosion value, surface modification, surface profile, local erosion value
Velocities and sizes of dust
particles, onset conditions;
parameters of films,
porosity and fractal structure, films thickness and density, chemical composition
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 9
Experimental resultsCFC NB31, PAN-fibers erosion
«PAN» fibers (6%)
«Needled PAN» fibers (2%)
Z
Y
X
Plasma flow
«pitch»fibers
(25-30%)10 mm
PAN fiber damage is a main mechanism of CFC erosion under ELM-like and disruption-like plasma load
100 мкм
Q = 1MJ/m2, Δt=0.5 ms, N=100 pulses
Pitch fibers PAN fibers
Forschungszentrum Jülich
J.Linke, T.Hirai
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 10
After 500 pulses
Q0=0.5 MJ/m2
Plasma flow direction
CFC erosionPAN-fibers erosion measurement
PAN-fiber erosion value measured along the target surface is correlated to the measured value of absorbed energy density. This correlation allow to define PAN-fiber erosion rate as a function of heat load.
After 5 pulses
Q0=2.3 MJ/m2
Measurement points
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 11
CFC erosion Comparison of experimental and modeling results
PAN-fiber erosion increase from 0.01 μm/pulse to 10 μm/pulse in the heat load range of 0.2-2.4MJ/m2
Numerical modeling(code PEGASUS-3D)
Forschungszentrum Karlsruhe (I.S. Landman, B.N. Bazylev, and S.E. Pestchanyi)
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 12
Tungsten erosion Pure W. Crack formation. Primary and secondary cracks
W, 1MJ/m2, 20 pulses
1mm
100 pulses
1mm
Secondary cracks: depth 50 µm
Primary crack: depth 500 µm
Forschungszentrum Jülich
J.Linke, T.Hirai
W, Q=1MJ/m2, 100 pulses
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 13
Numerical simulation PEGASUS-3D. Cracks formation.
Forschungszentrum Karlsruhe (I.S. Landman, B.N. Bazylev, and S.E. Pestchanyi)
Primary cracks (at a depth of 200 μm)
Secondary cracks (on the surface)
Secondary cracks
500 µm 100 µm
200 µm
GrainPrimary cracks
Numerical simulation(cod PEGASUS-3D)
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 14
Tungsten erosion Another type of cracks: cracks of the remelted W-1%La2O3
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 15
Tungsten erosion Dust generation as a result of cracking
crack width 10µm
Small tungsten dust particles
Melt layer delamination
100 µm
W-1%La2O3
W, Q=1MJ/m2, 100 pulses
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 16
Q, MJ/m2
X, cm
Y,
cm
Plasma flow direction
Experimental resultsCombined target (W+CFC), disruptions, Q0 = 2.3MJ/m2
-6 g/m2/pulse(mass loss)
-60 g/m2/pulse(mass loss)
-80 g/m2/pulse(mass loss)
+25 g/m2/pulse(mass growth)
W-1%La2O3
CFC NB31 CFC NB31Pure W
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 17
a b
c d
100 µm
200 µm
50 µm
PAN-fibers area
pitch-fibers area
Experimental resultsCombined target, Q = 2.3MJ/m2
20 µm
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 18
Dust investigation Dust collectors
18
Polished silicon substrates
Polished silicon substrates
Polished tungsten substrates
Traps of solid particles
Fitting elements
Copperplates
Particle flow
а б
The modernized target vacuum chamber allow to place various dust collectors and dust traps
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 19
Chamber 2Chamber 1
Plasma flow
Target
Collectors circles Collectors lines
Dust investigation Scheme of dust collectors placement
Polished silicon substrates
Polished tungsten
substrates
• The dust films deposit mainly after the target in plasma flow direction on the cooled part of vacuum chamber
• The maximum rate of film growth observed on disruption simulation experiment is equal to 0.4 μm/pulse
After 5 pulses
Combined target
W+CFC
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 20
Dust investigation Various dust structures, W+CFC, disruption experiments, Q=2.3MJ/m2
5 µм
1 µм
5 µм
2 µм
Cauliflower-like structure
100 µм
20 µм
Crystallite structureAmorphous films
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 21
Dust investigation Combined target (W+CFC). Size distributions of deposited particles,
10 µм
100 µm
Tungsten droplets on the CFC PAN-
fibers area
Cauliflower-like structure on the dust collectors
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 22
Y
XPlasma flow direction
DiagnosticsOnline diagnostics for droplets and particles ejection study
Pure tungsten, Qabs = 1.2 MJ/m2 , p = 1.8 atm
The scheme allows to define:• threshold plasma loads for dust particles ejection
starting;• components of the dust particle velocity vector;• absolute velocity value and flight angle of the
particle;• point of time formation and size of the dust particle.
The scheme of diagnostics
.2)()(
)(
,)()(
)(
0
2
0
0
0
tvz
gttvy
ftytz
ftyktY
tvz
tvxftx
tz
ftxktX
z
y
z
x
x(t), y(t), z(t) – droplets coordinates
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 23
Droplets ejection study Droplet ejection, pure tungsten, energy density Q = 1.6 MJ/m2
Surface of
the sample
Plasma stream
direction γ x
y v
z
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 24
SummaryCFC erosion
• PAN-fiber erosion is the main CFC erosion process under ITER-like transient plasma heat loads.
• The distribution of PAN-fiber erosion is determined on the CFC surface and related to the absorbed energy density distribution.
• The value of PAN-fiber erosion increases from 0.01 to 10 μm/pulse with a heat load in the range of 0.2-2.4 MJ/m2 according to the following law ΔhPAN = 0.9Q2.7.
• The amount of PAN-fiber erosion under plasma action correlates with results from numerical calculations taking vapor shielding and thermal conductivity degradation into account.
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 25
SummaryW erosion
• Crack formation is the main W erosion process under ITER-like transient plasma heat loads below the tungsten melting threshold.
• Primary cracks with a significant depth of up to 500 µm (after 100 pulses) form a grid on the surface with 1-3 mm characteristic cell size.
• Secondary cracks reach a depth of up to 50 µm (after 100 pulses) and form a surface grid with 100-300 µm characteristic cell size.
• The width of primary and secondary cracks increases with number of pulses.
• The cracks observed on the lanthanum tungsten remelted surface form a grid with cell sizes in the range from 1-100 µm and a melt layer thickness dependent depth.
I-7, G. Pintsuk, Forschungszentrum Julich 19 PSI, 2010 26
SummaryW erosion
• Melt layer movement and droplets ejection are the main W erosion processes under ITER-like transient plasma heat loads higher than the tungsten melting threshold.
• The main part of the droplets (>80%) follow the plasma flow direction at an angle between target surface and velocity vector in the range from 0 to 600.
• The absolute droplets velocity was determined to be in the range from 0 to 25 m/s.
• As a result of the exposure of combined W and CFC targets the mass of CFC target increased due to tungsten deposition and accumulation.